1. Field of the Invention
The present invention relates to a method for forming a fiber-reinforced composite material and, if desired, molding the same.
2. Description of the Prior Art
Known techniques for producing fiber-reinforced composite materials containing a thermoplastic resin as a matrix by compression molding include, for example,
(a) a method which comprises melting a resin using an extruder or the like, mixing the resin with reinforcing fibers, pre-molding the mixture into pellets, and then compression-molding the pellets in a mold (as disclosed, for example, in British Pat. No. 1,268,755),
(b) a method which comprises placing a mixture of a powdery or pelletized polymer and a reinforcing fibrous material in a mold, and compression-molding the mixture (as disclosed, for example, in Polymer Engineering and Science Vo. 3 No. 6, p. 455-461, (November 1973)), and
(c) a method which comprises mixing a reinforcing fibrous material and a powdery polymer utilizing an air flow, collecting the mixture on a net to form a mat, and molding the mat under heat and pressure (as disclosed, for example, in Japanese Patent Publication No. 44148/76).
These prior methods, however, present one or more difficulties. According to method (a), the fibers are cut to very short lengths during the mixing, and therefore, cannot fully exhibit a reinforcing effect. With method (b), it is difficult to mix the fibers uniformly with the polymer. Even if uniform mixing can be achieved, the components tend to separate before molding, and the uniformity of the molded product is not satisfactory. According to method (c), the powdery polymer often passes through the mesh of the collecting net, or the mixed powdery polymer tends to separate before molding, as is the case with method (b).